Directive helical antenna having integral balun-feed



July 26, 1966 E. SPlTZ 3,263,233

DIRECTIVE HELICAL ANTENNA HAVING INTEGRAL BALUN-FEED Filed May 6. 1965 United States Patent 3,263,233 DIRECTIVE HELICAL ANTENNA HAVING INTEGRAL BALUN-FEED Erich Spitz, Paris, France, assignor to CSF-Compagnie Generaie de Telegraphic Sans Fil, a corporation of France Filed May 6, 1963, Ser. No. 278,281 Claims priority, application France, May 7, 1962, 896,631 2 Claims. (Cl. 343-895) The present invention relates to directive antennas.

Directive antennas are known comprising a two-wire line about which a helix-shaped metal conductor is wound.

The width 0 of the radiation lobe 3 db below the maximum of such an antenna is given by the relation where L is the length of the antenna and A the operating wave length. For an angle 6 of 20, L=10 For a frequency of 400 mc./s., i.e. for 1:0.75 m., the length of the antenna is 7.50 m.

Such a length is not acceptable under certain conditions.

It is an object of the invention to provide an antenna of the above type, having a reduced length and the same performance.

The antenna according to the invention presents the following remarkable features:

(a) The antenna is excited by a transmission line, the outer conductor of which constitutes one of the elements of the antenna itself, coupling means being provided between this transmission line and the remainder of the antenna.

(b) The antenna comprises a reflector through which extends the transmission line. I

The invention will be best understood from the followign description and appended drawing, the only figure of which shows diagrammatically an embodiment of the antenna.

The antenna comprises of a two-wire line, comprising elements 1 and 2.

This line is surrounded by a metal helix 3.

Element 1 is the external conductor of a coaxial line, which is excited at one end by a source 7. The inner conductor 6 terminates at the opposite end by a junction element 5, which is, for example, welded to element 2. The coaxial line 1-6 extends through a reflector 4 and oscillator 7 is positioned at the other side thereof.

The operation of the antenna is as follows:

Oscillator 7 feeds, through the coaxial line 1-6, the junction element 5 which excites the two-wire line 1-2.

The effect is the same as if oscillator 7 were located at 5. The antenna built up by the two wire line 1-2 and the helix 3, is then excited.

On account of the presence of reflector 4, it operates as an antenna which would have a double length.

Of course, the antenna may also operate as a receiver antenna.

The antenna according to the invention presents the following advantages:

(a) Its length is reduced by half as compared to known antennas of this type. It may be used in commercial television as a receiver antenna on the roof of a building. For a frequency of 400 mc./s., its length is 5A=3.75 m.

(b) No symmetrical-dissymmetrical transformers are required, which are expensive and reduce the pass-band.

Of course, the invention is not limited to the embodiment shown which is given solely by way of example.

What is claimed, is:

1. A directive antenna comprising: a two-wire line including two wires; a helix wound around said line; a coaxial line having an outer and an inner conductor and two ends, said outer conductor serving as one of said wires; an ultra-high frequency source coupled to one of said ends; and means coupling said inner conductor to the other wire.

2. A directive antenna comprising: a two-wire line including two wires; a helix wound around said line; a coaxial line having an outer and an inner conductor and two ends; said outer conductor serving as one of said wires; an ultra-high frequency source coupled to one of said ends; means coupling said inner conductor to the other wire; and a reflector positioned at said one end.

References Cited by the Examiner UNITED STATES PATENTS 2,945,227 7/1960 Broussaud 343-895 X 3,113,316 12/1963 Berry 343792.5

OTHER REFERENCES Kraus: Antennas, McGraw Hill, N.Y., 1950, page 314.

Forbes: An Endfire Array Continuously Proximity- Coupled, AFCRC-TR-59-368, December 1959, page iii, 1, 2.

Sodaro: Helical Antenna Design, Radio-Electronic Engineering, February 1954, page 40.

HERMAN KARL SAALBACH, Primary Examiner.

P. L. GENSLER, Assistant Examiner. 

1. A DIRECTIVE ANTENNA COMPRISING: A TWO-WIRE LINE INCLUDING TWO WIRES; A HELIX WOUND AROUND SAID LINE; A COAXIAL LINE HAVING AN OUTER AND AN INNER CONDUCTOR AND TWO ENDS, SAID OUTER CONDUCTOR SERVING AS ONE OF SAID WIRES; AN ULTRA-HIGH FREQUENCY SOURCE COUPLED TO ONE OF SAID ENDS; AND MEANS FREQUENCY SOURCE COUPLED TO ONE OF SAID OTHER WISE. 